A data transfer amount of a wireless network has been rapidly increased in recent years. It is because various devices, e.g., a smart phone, a tablet personal computer (PC), or the like, that require machine-to-machine (M2M) communication and a high data transfer amount have been introduced and propagated. To satisfy the required high data transfer amount, a carrier aggregation (CA) technique, a recognition radio technique, or the like for effectively using more frequency bands, and a multiple antenna technique, a multiple base station cooperation technique, or the like for increasing data capacity within a limited frequency have recently drawn attention.
In addition, the wireless network has been evolved in a direction of increasing density of a node capable of accessing to an area around a user. Herein, the node implies an antenna (or antenna group) which is separated from a distributed antenna system (DAS) by a certain distance or farther. However, the node is not limited to this definition, and thus can also be used in a broader sense. That is, the node may be a pico-cell eNB (PeNB), a home eNB (HeNB), a remote radio head (RRH), a remote radio unit (RRU), a relay, a distributed antenna, etc. From UE perspective, UE may recognize a node in a logical sense, not a physical node itself. UE can recognize a node by the reference or pilot signal that the node transmits. Accordingly, a reference or pilot signal can represent a node no matter how the reference or pilot signal is transmitted physically. Therefore, the terminology ‘node’ includes logical node as well as physical node.
A wireless communication system having such a node with higher density can provide higher system performance by cooperation between nodes. That is, better system performance can be achieved when one base station controller manages transmission and reception of respective nodes and thus the nodes operate as if they are antennas or an antenna group for one cell, in comparison with a case where the respective nodes operate as an independent base station (BS), advanced BS (ABS), node-B (NB), eNode-B (eNB), access point (AP), etc., and thus do not cooperate with each other. Hereinafter, a wireless communication system including a plurality of nodes is referred to as a multi-node system.
If each node of the multi-node system performs scheduling and handover by having its own identifier (ID), then such a multi-node system can be regarded as a multi-cell system. If each cell (i.e., node) of the multi-cell system has overlaid coverage, such a multi-cell system is called a multi-tier network.
The multi-node system can operate according to two methods, that is, a method 1) in which the multi-node system can be utilized as a multi-cell system by assigning a different cell ID to each node and a method 2) in which all nodes can operate as one cell while operating as a virtual cell by assigning a common cell ID to each node. The virtual cell implies a device which is not recognized as an independent node in a legacy user equipment (UE), but is recognized as an independent node in an advanced UE. For example, a UE that operates based on 3rd generation partnership project (3GPP) long term evolution (LTE) can be the legacy UE, and a UE that operates based on an LTE-advanced (A) can be the advanced UE.
In a case where the multi-node system operates according to the method 2) above, the UE has to know a transmission parameter of each virtual cell in order to receive a virtual cell specific signal. A method of directly reporting all transmission parameters of the virtual cell results in significant increase in signaling overhead.
Accordingly, there is a need for a method and apparatus for receiving a virtual cell specific signal by a UE in a multi-node system.